Why are more and more leopard sharks stranded on Indonesian beaches?

content

2 months ago

Jakarta, domclub Indonesia
—
Case
spotted shark
or whale shark (
Rhincodon typus
) stranding on the Indonesian coast has happened again.Finally, a long spotted shark with a length of around 4 meters and weighing around 1 ton was found dead and stranded on Pagak Purworejo Beach, Central Java on Sunday (7/12).
This case adds to the long list of cases of leopard sharks stranded on Indonesian beaches.Throughout 2025 alone, a number of cases of leopard sharks being found dead stranded on various Indonesian beaches were recorded, from Muara Mati Bekasi, Bunton Beach Cilacap, to Pangi Beach Blitar.
ADVERTISEMENT
SCROLL TO CONTINUE WITH CONTENT
This phenomenon is not an isolated incident, but rather part of an increasingly worrying pattern.So, why are leopard sharks found stranded more frequently in Indonesia?
A study entitled ‘
Spatio-temporal patterns, trends, and oceanographic drivers of whale shark strandings in Indonesia
‘ which appeared in
Scientific Reports
on October 17 2025 even revealed that leopard shark strandings on Indonesian coasts have increased in recent years.
“In Indonesia, most cases of leopard shark strandings were initially reported as animals swimming near the coast, but were not actually stranded,” the researchers wrote in the study, reported Monday (8/12).
“In most cases, although still alive, weakened leopard sharks are unable to return to a suitable depth and are often pulled to shore by well-meaning villagers, resulting in their death,” he continued.
Researchers recorded 115 cases of leopard shark strandings in Indonesia in the last 13 years, involving 127 individuals in 23 of Indonesia’s 38 provinces.
The researchers concluded that of the 115 cases that occurred, the southern coast of Java was the location most prone to leopard shark strandings in Indonesia.
This study also shows that more than 70 percent of stranded whale sharks are juvenile individuals measuring 4-7 meters, because this age group often uses Indonesian coasts as a feeding area, so they are more often in productive shallow waters.
Considering that whale sharks only reach sexual maturity at 7-9 meters, the loss of juvenile individuals poses a serious threat to the sustainability of their population.
Reasons why leopard sharks get stranded
Researchers in their study found that the shark strandings were related to strong upwelling currents and may be related to the sharks’ seasonal foraging in the area.
The southern coast of Java experiences strong upwelling in June-November, bringing cold, nutrient-rich water masses to the surface.Rising ocean productivity triggers an explosion of plankton, small fish and krill, which attracts spotted sharks closer to shore.
High waves of more than 1.5 meters triggered by upwelling can push sharks towards coastal areas, while a drastic drop in sea temperatures to the range of 26-28 degrees Celsius has the potential to disrupt their navigation abilities.
“While natural events were identified as the primary factor contributing to leopard shark strandings, human activities may also play an important role and require further investigation,” the researchers said.
At the same time, the appearance of prey blooms around the coast can attract sharks too close to shallow water, increasing the risk of getting trapped and ultimately stranded.The statistical model (Negative Binomial GAM) shows that high waves are the most significant predictor for stranding events.
Sharks enter shallow areas when chasing fish (for example anchovies), but cannot return to the deep sea due to large waves or the shape of the sunken beach.These findings are consistent with reports of “prey hunting into shallow zones” in the journal.
Several stranding cases are also related to drift gillnets and drifts, similar to the Bekasi case, which causes stress, fatigue and even death.
Necropsy research in Kebumen in 2023 showed liver degeneration, kidney damage, as well as indications of exposure to toxins thought to come from pond waste and the eutrophication process, thus confirming that the quality of coastal waters has a major influence on the health condition of whale sharks.
(wpj/dmi)